SYNCHRONIZED ONSET OF NUCLEAR AND SURFACE CHANGES DURING APOPTOSIS OF HUMAN, RAT AND MOUSE LYMPHOCYTES
Dini L. and Abbro L.
Department. of Biological and Environmental Science and Technology, University of Lecce, Italy
Many morphological changes (i.e. cell shrinkage, cytoplasm and chromatin condensation, cell surfaces exposition of PS and normally hidden sugar residues) characterized lymphocytes apoptosis. In this study we investigated the relationship between nuclear and cell surface modifications in lymphocytes isolated from human, rat and mouse and induced to apoptosis with cycloheximide (CHX) 10-2M for 24hrs. Cells were monitored for their progressive accumulation of cell surface and morphological modifications. Three types of apoptosing lymphocytes, with different percentages, were found at all times of incubation with CHX irrespective of the species. Type 1 (early apoptosis): the majority of the cells showed no signs of apoptotic morphological modifications, although very few cells show mild margination of chromatin or the stereotypical apoptotic morphology. Increased PS and sugar residue expression on the cell surface were detected, independently of the nuclear modifications. Type 2 (mature apoptosis): the majority of cells showed extensive chromatin condensation and nuclear fragmentation and cellullar blebbing. Cell surface was highly modified, with extensive exposure of PS and sugar residues. Type 3 (late/necrotic apoptosis): almost all apoptotic cells underwent secondary necrosis. A decreased exposure of PS and abundant expression of sugar residues (i.e.fucose), absent from surface of early apoptotic lymphocytes were observed. Nuclei were for the most fragmented and the fragments were seen as micronuclei inside the dead cells, whose cytoplasm was largely vacuolized. When surface modifications are considered, differences were observed between human and rat lymphocytes and between rat and mouse lymphocytes, human and mouse lymphocytes being similar.
